The Real IRA last night issued a dramatic call to arms to republican terrorists who have doubts about Sinn Fein's approach to come under its banner and push for a united Ireland.

The statement fell short of announcing an imminent return to violence, but it did indicate that the hardline group was considering ending its ceasefire.

The Real IRA announced its cessation three weeks after killing 29 people and injuring 200 in a car bomb attack in Omagh, Co Tyrone, in August 1998. It was worst atrocity in 30 years of the Troubles.

The terror group, led by a former quartermaster of the IRA, called its ceasefire only after waiting to see whether the revulsion within republicanism which the Omagh massacre sparked would dissipate. Its statement 16 months ago was its last until now.

Security sources suggested last night's long recruitment statement - the first from a terror group ever to be delivered to the media via email - meant the Real IRA might soon call off its cessation. It instructed all volunteers to ensure the safety of civilians at all times, a grudging apology for the deaths at Omagh.

One view within republicanism was that the Real IRA's move would make it more difficult for the IRA to begin arms decommissioning. That would pile pressure on the fledging government in Northern Ireland, apparently one of the key aims behind last night's statement.

The group encourages all those doubting Sinn Fein's strategy to rally behind it, evoking the all-Ireland parliament of 1918. There are several swipes at mainstream republicans, labelling them "an elite clique, or corrupt treacherous administration."

But some republicans believe the Real IRA is so discredited that its move could entice the IRA to make a start to decommissioning. There is bad blood between the outfits, and there have been clashes.

While there have been defections to the Real IRA, the Irish police believe their recent operations, culminating in several arrests, have left the dissident group weakened and with dented credibility. They believe few IRA members are likely to defect. One Garda source discounted recent suggestions the Real IRA had doubled in strength to almost 200 members. He believed the figure remained between 80 and 100 members.

The Real IRA was formed when several leading IRA figures quit in September 1997 in opposition to Sinn Fein signing up to the Mitchell principles of peace and democracy to enter the multi-party talks at Stormont. It is opposed to the Good Friday agreement.

It has since attracted support from the small dissident group, Continuity IRA, linked to Republican Sinn Fein, and the Irish National Liberation Army.

It has also won the support of several well-respected IRA figures, particularly in border areas.

The statement says: "It would be remiss of Oglaigh na hEireann to abdicate our responsibility for the many innocent lives that have been lost and injuries occurred as a consequence of the ongoing struggle for freedom in the past century. It is incumbent on all volunteers to ensure the safety of non-combatants at all times."